Most mobile machines, such as an off-highway truck, include an operator cabin having a controlled environment that provides operator comfort. The machine generally includes an air-conditioning system to maintain the operator cabin at a desired temperature. These mobile machines are often required to work in ‘idle state’ for long periods of time during which the machine's engine is being used to power the air-conditioning system. For example, an off-highway truck may idle when a body of the truck is being loaded which often takes considerable amount of time. In some locations, however, idling for long periods of time may not be allowed for environmental reasons. And even if long periods of idling are allowed, doing so can be inefficient and costly. In these situations, the engine of the machine needs to be turned off, which in turn switches off the air-conditioning system and resulting in ambient conditions within the operator cabin that may be uncomfortable for the operator.
US Patent Publication No. 20120090823 (hereinafter referred to as '823 publication) relates to a storage heat exchanger with interstitial space filled with a material for storing calories. The '823 publication provides a main air-conditioning loop and a secondary loop arranged in a heat exchange relationship with the main air-conditioning loop. The secondary loop includes the storage heat exchanger, a pump for circulating fluid through the secondary loop, and a heat exchanger. An evaporator, in the main air-conditioning loop, provides the air-conditioning effect. The evaporator further allows the transfer of heat between refrigerant fluid circulating inside the main air-conditioning loop and the secondary heat transfer fluid circulating inside the secondary loop. Therefrom, the secondary heat transfer fluid transfers heat with the said material of the storage heat exchanger for providing air-conditioning effect when the main air-conditioning loop is stopped.
In the '823 publication, the use of same evaporator for air-conditioning as well as exchanging heat with the secondary heat transfer fluid limits the temperature control and heat transfer rate to the secondary heat transfer fluid. Further, the disclosed storage heat exchanger has a potential energy between 200 and 270 kJ. The size of the storage heat exchanger along with other physical features limits the heat transfer rate between the secondary heat transfer fluid and storage material. Thus, the disclosed system may primarily be applicable for air-conditioning of relatively small automotive vehicles using the storage heat exchanger, and may not be easily scalable to provide air-conditioning for large machines or the like.